On some cars, if you don't purchase an option like navigation, you'll have the option to pay for and enable it at a later date. Tesla's Autopilot suite of semi-autonomous driving aids is one such system, and in the event that you're still on the fence about dropping some more coin on your fancy electric car, Tesla's offering a trial period.

According to a post in Reddit's /r/teslamotors subreddit, Tesla models without Autopilot enabled are being offered one-month trial periods to check the software out. The trial gives you access to semi-autonomous steering, adaptive cruise control, semi-autonomous lane changing and the automaker's self-parking feature, Summon. (One Reddit user amusingly refers to it as "DLC for a car," in reference to video games' downloadable content.)

After the month is up, Model S and Model X owners will have the chance to spring for the software permanently. It costs $2,500 when you order a new vehicle, but if you want it installed after delivery, the price jumps to $3,000.

The vehicles in question come equipped from the factory with all the hardware required for Autopilot, many parts of which are integrated into other, standard safety systems (like automated emergency braking), so the cost goes toward enabling the remaining systems -- no additional installation required.